The present invention relates generally to the field of actuators for electronic circuit breakers, and more particularly to circuit breakers having an electronic trip unit and an external actuator coupleable to the electronic trip unit.
Some circuit breakers (e.g., molded case circuit breakers, or MCCBs) utilize a mechanical trip unit comprising, for example, a bi-metallic sensing element to sense trip conditions in a power signal, such as, overcurrent, ground fault, short circuit, etc. More modern circuit breakers utilize an electronic trip unit and current transformers. The current transformers sense one or more phases of the power signal and provide sense signals to the electronic trip unit. The electronic trip unit, typically using microprocessor controls, digitizes the sense signals and determines when a circuit breaker trip is needed based on detection of one of the trip conditions. The electronic trip unit then provides a trip signal to an actuator (e.g., a mag-latch) which provides the necessary force to trip the mechanical operating mechanism which, in turn, provides a break in the power line.
In some electronic circuit breakers, the mechanical trip unit is removable from the circuit breaker casing or frame. Thus, the mechanical trip unit can be replaced with a new mechanical trip unit or even an electronic trip unit. Also, a mechanical interlock has been provided to assure that the electronic trip unit is properly coupled to the frame of the circuit breaker.
One challenge in designing electronic circuit breakers is to provide all of the necessary and desirable functionality, including testing functions, sense signal amplifiers, actuators, operator input devices, and operator displays, in a limited amount of space. Since the mag-latch is a large component, it has been proposed to remove the mag-latch from the electronic trip unit and package the mag-latch for installation on the circuit breaker separate or external from the electronic trip unit. However, one drawback of having an external mag-latch is that the mag-latch must be properly installed and all electrical connections between the mag-latch and the electronic trip unit must be complete for the circuit breaker to function properly. Also, the mechanical connections between the mag-latch and the operating mechanism must also be complete for the circuit breaker to function properly.
An improved circuit breaker is needed which will verify the coupling of a mag-latch or other actuator to a circuit breaker having an electronic trip unit. The mag-latch would be easily installable without the use of additional fasteners and not require complex testing systems or circuitry to verify the proper installation of the mag-latch. The mag-latch would also allow easy removal of the electronic trip unit without removing the mag-latch. The mag-latch would also provide communication between the electronic trip unit and the contacts of the operating mechanism.
One embodiment relates to a circuit breaker having a sensing circuit, a control circuit, an actuator, an operating mechanism, and an interlock mechanism. The sensing circuit is configured to generate the sense signal representative of a power signal flowing through a power circuit. The control circuit has a frame and is configured to receive the sense signal and to provide a trip signal on a first terminal. The actuator is external to the control circuit frame and has a second terminal coupleable to the first terminal. The actuator is configured to receive the trip signal on the second terminal. The operating mechanism is coupled to the actuator and is configured to open and close the power circuit in response to actuation of a lever. The actuator is configured to actuate the lever in response to the trip signal. The interlock mechanism is coupled to at least one of the actuator and the operating mechanism and is configured to actuate the lever when the first terminal is not coupled to the second terminal.
Another embodiment relates to a circuit breaker having sensing means for generating a sense signal representative of a power signal flowing through a power circuit, control means for receiving the sense signal and for generating a trip signal based on the sense signal, and trip means for opening and closing the power circuit. The circuit breaker has a first means for receiving the trip signal and for tripping the trip means and a second means for determining whether the first means is coupled to the control means and for tripping the trip means when the first means is not coupled to the control means.
Yet another embodiment relates to a method of interlocking an actuator to a circuit breaker, the circuit breaker having a sensing circuit configured to generate a sense signal representative of a power signal flowing through a power circuit, a control circuit configured to receive the sense signal and to provide a trip signal on a first terminal based on the sense signal, an actuator external to the control circuit frame having a second terminal coupleable to the first terminal, and an operating mechanism configured to open and close the power circuit. The method includes receiving the trip signal and tripping the operating mechanism when the trip signal is received, determining whether the first terminal is coupled to the second terminal, and tripping the operating mechanism when the first terminal is not coupled to the second terminal.
Still another embodiment relates to an interlock mechanism for a circuit breaker having a control circuit and an actuator, the control circuit configured to provide a trip signal to the actuator, the actuator configured to trip the circuit breaker in response to the trip signal. The interlock mechanism includes a first connector coupled to the circuit breaker, the first connector having a first terminal and configured to receive the trip signal. The interlock mechanism also includes a second connector coupled to the actuator, the second connector having a second terminal and configured to receive the trip signal from the first terminal. One of the first and second connectors includes a protrusion and the other includes a resilient member biased toward the protrusion having a first and second position. The resilient member is coupled to a trip lever and the resilient member trips the circuit breaker via the trip lever only when the protrusion is in the first position.